1. Field of the Invention
This invention relates to retinal reattachment surgery, and more particularly to a method which uses laser induced scleral shrinkage and transscleral photocoagulation to facilitate retinal reattachment.
2. Background Information
Retinal detachment is one of the leading causes of blindness. It affects approximately one in every 15,000 people in the general population per year or an estimated 0.3% over a life-time.
Typically, retinal reattachment surgery includes the following steps: (1) conducting a thorough preoperative examination with the goal of identifying all retinal breaks and assessing any vitreous traction on the retina; (2) dissecting the conjunctiva over 360.degree. to expose the sclera; (3) freeing the muscles of Tenon's capsule; (4) identifying and marking retinal breaks using binocular indirect opthalmoscopy and scleral depression; (5) creating a controlled injury to the retinal pigment epithelium (RPE) and retina by means of cryotherapy (cryopexy), photocoagulation, and diathermy to induce a chorioretinal adhesion (adhesion produced by wound healing) at the site of all retinal breaks; (6) when necessary, draining the sub-retinal fluid (accomplished in many instances by using a needle-shaped diathermy electrode to prevent possible choroidal hemorrhage); (7) employing all appropriate technique, such as scleral buckling and/or intravitreal gas (e.g. air, SF6, C3F8) injection or silicone oil (polydimethyl-siloxane, etc.) vitreous substitution to approximate (tamponade) the retinal breaks to the underlying retinal pigment epithelium; and finally, 8) approximating and suturing the dissected conjunctiva. Scleral buckling surgery requires significant manipulation of the eye, causes (intraoperatively) a rapid and fluctuating intraocular pressure rise (.gtoreq.200 mmHg), and is time consuming. Rehabilitation from such surgery is from one to four days. Furthermore, scleral buckling has been associated with recurrent proliferative vitreoretinopathy (PVR), a complication that is difficult to treat.
The purpose of the buckle is to create enough scleral indentation (bump) for the choroid to approximate the detached retina following subretinal fluid drainage. Most buckling surgical procedures require a great deal of surgical incisions and dissections to position the implant that has to be sutured to the sclera in order to create a stable and adequate buckling effect. The implant, also known as an exoplant, may be made, for example, of several forms of silicone (solid, sponge or foam) rubber, of hydrogels or, in poor countries, fascia lata.
Since a high percentage of retinal detachment patients are myopic, conventional buckling surgery may induce more myopia and astigmatism since the surgery has a tendency to elongate the total length of the eye (increase the eye's axial length). More importantly, current surgical techniques have very limited applications to some difficult pathological conditions such as staphylomata, caused by high myopia, where the sclera is very thin and can hardly support dissections and sutures.
Chorioretinal adhesion is induced either by RF diathermy, cryopexy or photocoagulation. RF diathermy has been shown to cause more postoperative complications than the other two techniques, and has largely been abandoned for treatment of retina detachments. The cryogenic probes (-70.degree. to -90.degree. C. tip temperature, application time of .apprxeq.5s) used in retinal cryopexy are bulky, inflexible, and produce unnecessary large damage to scleral tissue and underlying structures. Retinal photocoagulation is the preferred method to produce chorioretinal adhesion normally performed ab interno, by focusing the energy of a continuous-wave (cw) Argon, a cw Krypton, or a cw diode laser, etc., through the patient's cornea and pupil, onto the retina. The laser delivery systems in common use are the operating microscope and the indirect ophthalmoscope for intraoperative treatment, when the patient is in the supine position, and the slit-lamp for postoperative treatment, when the patient is in the sitting position. Should an intraocular procedure such as vitrectomy or retinotomy be required to unfold and re-approximate the retina to the choroid, then retinal photocoagulation is normally performed intraoperatively using a fiber optic probe inserted in the vitreous cavity, a procedure known as "endophotocoagulation". Recently, intraoperative and postoperative retinal photocoagulation has also been performed ab externo (transsclerally) using the energy produced by a cw Nd:YAG laser (Neodymium: Yttrium Aluminum Garnet; wavelength=1.06 .mu.m or a C. W. Diode Laser (808 nm)) conducted through a fiber optic probe applied to the sclera overlying the retina break.
Conventional scleral buckling procedures require extensive surgical manipulations, implantation of a device and may require the use of an expensive laser system to produce chorioretinal adhesion. Since mechanical buckling increases the length of the eye, as noted above, a patient with a successfully reattached (and intact) retina, may nevertheless require spectacles or contact lenses to regain adequate vision.
Accordingly, it can be appreciated that a need exists to provide a simplified and more advantageous surgical method of retinal reattachment using light to shrink scleral tissue to produce a "buckle".